I was reading the relative/pegged-to-primary order type offered by IB. If I understand it correctly, it generates an order that is better than NBBO by an offset and follows the change in NBBO. Imaging there are two users submitting this type of order to buy the same security, would they compete with each other by continuously bidding up the NBB? For example: NBBO is $10.10 x $10.20 User A submits a relative order with offset $0.01, bidding at $10.11. Now NBBO is $10.11 x $10.20 User B submits a relative order with offset $0.01, bidding at $10.12. Now NBBO is $10.12 x $10.20 User A's order adjusts automatically to $10.13 User B's order adjusts automatically to $10.14 ... Obviously this can't happen in practice. What did I get wrong?